I quite like the look of it, as it's consistent throughout the OS compared to prior version of iOS. Even though I didn't mind skeuomorphism, in fact for certain types of programs I think it's more appealing/better suited (makes them more fun or helps convey more information). However across an OS I don't think it works.

So I'm a little disappointed with some of the design changes to a couple of apps, but overall it's for the best.

It's also nice they went for a flat look as the current app I'm working on has a flat UI, as well as lot of the other points they mention in their new design guidelines. So saves me a bunch of work :).

I haven't upgraded to it as of yet, and probably won't. I most likely will wait until it reaches GM seed.

EDIT: Also as far as markdown vs BBCode, markdown also tends to makes more sense structurally. I think the forum should just pick one and use only that.